The present invention relates to an arrangement for the coaxial fastening of an input component of a clutch, such as a friction clutch, to a crankshaft of an internal combustion engine of a motor vehicle.
Ordinarily, conventional friction clutches of motor vehicles comprise a one or two-part flywheel, to which a pressure plate unit is fastened by screws. The pressure plate unit comprises an axially movable pressure plate that is rotationally fixed to but axially movable on a clutch housing fastened to the flywheel by screws and is preloaded by a main clutch spring, usually a diaphragm spring, toward the flywheel. The pressure plate and the flywheel form friction surfaces for a clutch disc positioned between them. The clutch disc has a hub that is rotationally fixed to but axially movable on an input shaft of a transmission in the drivetrain of the motor vehicle. The flywheel is fastened by screws to an end flange of the engine crankshaft by a plurality of screws arranged concentrically to the axis of rotation of the crankshaft.
In conventional friction clutches, the clutch disc and the diaphragm spring overlie in the axial direction the screws that attach the flywheel to the end flange of the crankshaft. Therefore, in assembly of the friction clutch, the flywheel must first be fastened to the crankshaft end flange before the clutch disc can be put in place and the pressure plate unit screwed to the flywheel. This assembly process is not only time-consuming, but also has the disadvantage that the friction clutch as a whole, i.e., including the clutch disc and the flywheel, cannot be inspected for compliance with specifications before assembly.
German Published Patent Appln. No. 4,117,571 discloses an arrangement in which the clutch disc and the diaphragm spring are provided with holes which are aligned axially with the screws for fastening the flywheel to the end flange of the crankshaft. In this way the pressure plate unit can be assembled to the clutch disc and the flywheel into a preassembled unit (a modular clutch) before installation on the crankshaft. The fastening screws may be screwed into the end flange of the crankshaft through the holes of the clutch disc and the diaphragm spring.
In German Published Patent Appln. No. 3,315,232, it is proposed that a modular clutch, consisting of flywheel, pressure plate unit and clutch disc, in which the clutch housing and the flywheel are preassembled non-detachably, be fastened to the output end of the crankshaft by means of a central screw. The output end of the crankshaft has a threaded hole for receiving a screw. The screw has a flange projecting radially, which tightens the flywheel against the axial end face of the output end of the crankshaft. The screw is hollow and receives a pilot bearing, which radially carries the engine-side end of the transmission input shaft that passes through the hub of the clutch disc. However, the torque transmissible through the radial flange of the screw is comparatively low, since the screw can only sustain limited starting torques.
It is disclosed in German Published Patent Appln. No. 4,013,298 that for fastening the flywheel of a modular clutch, the axially facing faces of an end flange of the crankshaft and of the flywheel may be provided with a radial toothing (Hirth-type serrations) and the flywheel in turn be fixed axially to the output end of the crankshaft by a central screw that also receives the pilot bearing of the transmission input shaft. In this case, the screw only takes care of axial fixation, while the torque is transmitted to the flywheel by means of the radial toothing of the crankshaft. The screw, which is screwed into a central threaded opening of the output end of the crankshaft, is provided in the region of the pilot bearing with central key faces into which a screwdriver can be inserted through the hub of the clutch disc in order to tighten the screw on the crankshaft.
Lastly, it is disclosed in the book by K. Wiecking and R. Gebauer, "Die Motoren der Personenkraftwagen" [Engines of Passenger Vehicles], Verlag Chr. Belser, Stuttgart, 1952, page 314, figure 341, that the flywheel of a conventional friction clutch may be fastened by means of a cone compression coupling at the output end of the crankshaft of the internal combustion engine. The output end bears an external cone, tapering toward the clutch disc, on which the flywheel is seated by an internal cone of its hub. The output end of the crankshaft terminates in a threaded pin, on which is screwed a nut securing the flywheel. However, the known design does not make it possible to install the pressure plate unit together with the clutch disc and the flywheel as a preassembled unit.